Thread by @kerpen

Friday Fluday Thread: Influenza-Like Illness Data for MMWR Week 18, ending May 8, 2021

United States Influenza testing, MMWR week 18.

CDC flu view. cdc.gov/flu/weekly/ind…

2016 to 2019 4-year average: 853 cases; 7.09% positive

2020: 46; 0.57%
2021: 23; 0.07%

docs.google.com/spreadsheets/d…

United States Influenza testing, season to date (32 weeks, MMWR 40 to 18)

Five-year average: 208,466 cases; 18.28% positive

This year: 2,097; 0.14%

Season-to-date U. S. flu hospitalizations down 98.9% from last year.

Flu hospitalizations (32 weeks) in FluSurv-NET catchment is 226 (+0 from last week). Through week 18 last year (31 weeks) it was 20,094 (+56).

Rate last year: 69.2 per 100K
This year: 0.8 per 100K

Influenza-Like Illness (ILI) continues to be historically low after a skied season; ticked up this week (HCoVs?).

Latest U.S. non-SARS-CoV2 syndromic data from BioFire.

Lots of rhinoviruses (just ticked down, potential peak forming?) and some adenoviruses all year.

Flu A, B micro-wave already over. RSV, and PIV back at low levels.

HCoVs comeback continues.

syndromictrends.com

Out-of-season HCoV wave continues.

HCoV NL-63 appears post-peak but has turned back up. HCoV-OC43 still rising sharply. HCoV-229E rising at lower levels. Last year's dominant HCoV-HKU1 still near zero.

Here are the HCoVs with SARS-CoV2, from Biofire's newest respiratory panel.

SARS-CoV2 peaked and declined as the HCoVs re-appeared and rose.

CDC data shows the same picture. cdc.gov/surveillance/n…

CDC HCoVs by region. cdc.gov/surveillance/n…

Florida. Schools open all year. No lockdowns since September. Rhinoviruses and adenoviruses all year.

Flu declined in the one region that had any.

ILI remains flat.

RSV ED visits flat; finally a peak?

floridahealth.gov/diseases-and-c…

Sweden week 18. No masks, no lockdowns, no school closures under age 16 -- and a full year with no Flu A, Flu B, or RSV; RSV ticks up again after reappearing finally four weeks ago. HCoVs flat, remain higher than seasonal norm after long absence.

karolinska.se/globalassets/g…

Germany week 18. Rhinoviruses tick back up. Slight decrease for HCoVs and decrease for SARS-CoV2, first time in 5 weeks they haven't moved in opposite directions.
influenza.rki.de/Wochenberichte…

Brazil. Very lax control measures, and a president who urges people to disregard them. A completely skipped flu season.
apps.who.int/flumart/Defaul…

The global flu chart from WHO.
apps.who.int/flumart/Defaul…

The exceptions.
apps.who.int/flumart/Defaul…

It wasn't masks, which were never used in many countries where flu disappeared and have also been shown to be ineffective for stopping influenza in many, many studies.

apps.who.int/iris/bitstream…

Japan masks every year, and pushed masks hard in 2019 with no apparent effect. But in 2020-21 flu disappeared with low stringency COVID intervention.
apps.who.int/flumart/Defaul…

The idea mitigations worked but unmitigated SARS-CoV2 just has a higher R (popular now among the same crowd that still said "twindemic!" when flu had been gone for months, like Anthony "mask seasonally" Fauci) is way too facile.

Outside of testing ramp up, I don't think we've seen R > 2, even in places without NPIs.

Rhinoviruses bounced right back despite lower R and RSV was gone until recently with comparable R to SARS-CoV2.

HCoVs were gone until SARS-CoV2 declined, then returned even with lockdown.

Plus, as Biden adviser Dr. Michael Osterholm admitted, our mitigation just hasn't been very effective.

Maybe in places like Australia and New Zealand where mitigations stopped SARS-CoV2 they also stopped other viruses.

But in countries where SARS-CoV2 went wild? No.

Osterholm: "There is this viral interference"

Viral interference is a well-known (but poorly understood) phenomenon. Interference from rhinovirus is generally thought to have ended the swine flu epidemic in 2009.
thelancet.com/journals/lanmi…

This great short article from @m_soond explains the viral interference theory of this respiratory season.
medium.com/illumination-c…

Overall the season has been so mild that drug store chains took big losses.

Rite Aid CEO Heyward Donigan: "During the fourth quarter our industry was impacted by a historically soft cough, cold and flu season."
forbes.com/sites/brucejap…

Pediatric internships and residencies have to be extended or supplemented because they just didn't have enough patients to gain the normal amount of clinical experience.
aappublications.org/news/2021/03/1…

CDC still reports just one pediatric flu death this season.

The numbers in chart in previous tweet are lab-confirmed only, but flu testing is very limited (see totals at top of thread) so CDC also publishes best estimates of total pediatric flu deaths.
cdc.gov/flu/about/burd…

COVID testing is much, much more abundant than flu testing and the definition of deaths typically used (any cause of death within 30-60 days of a positive test result) tends to overcount.

Per CDC, 2.5% of all death certificates in the COVID count have a cause of death that cannot plausibly be connected to COVID.

But that figure is much higher for younger age groups: 35.2% under age 18 and 10.2% 18 to 29.

cdc.gov/mmwr/volumes/7…

Keeping that in mind, this table compares CDC best estimates of pediatric flu deaths with the first two seasons of pediatric COVID deaths as reported.

(Note that everywhere in the world where COVID was epidemic, it circulated *instead of*, not in addition to, influenza.)

We are now near the end of the *safest* respiratory season for children ever recorded. (Including places where schools never closed and nobody masked.)

Yet many places locked children out of school, and some places are still doing so. Many more kids are masked.

It's a disgrace.